The present invention relates to a control system for a throttle valve actuating device including a throttle valve of an internal combustion engine and an actuator for actuating the throttle valve.
One known throttle valve opening control system for a vehicle is disclosed in Japanese Patent Laid-open No. Hei 8-261050. In this control system, an opening of a throttle valve which is actuated by a motor is controlled with a PID (Proportional, Integral, and Differential) control, and control constants of the PID control is set according to an operating condition of the vehicle.
However, since the throttle valve actuating device, which is a controlled object, has non-linear characteristics, there remains room for improvement, according to the conventional PID control, in control accuracy, control stability, and a follow-up characteristic (convergence characteristic) of the throttle valve opening to a target value.
It is therefore an object of the present invention to provide a control system for a throttle valve actuating device, which can improve control accuracy, control stability, and a follow-up characteristic of the throttle valve opening to a target value.
To achieve the above object, the present invention provides a control system for a throttle valve actuating device (10) including a throttle valve (3) of an internal combustion engine and actuating means (6) for actuating the throttle valve (3). The control system includes control means (21) for controlling the throttle valve actuating device based on a controlled object model so that an opening (TH) of the throttle valve (3) coincides with a target opening (THR). The control object model is defined by modeling the throttle valve actuating device (10).
With the above configuration, the throttle valve actuating device is controlled based on the controlled object model obtained by modeling the throttle actuating device. By controlling the throttle valve actuating device based on the controlled object model, the follow-up characteristic of the throttle valve opening to the target opening can be greatly improved compared with the conventional control methods such as the PID control. Further, control accuracy and control stability are also improved.
Preferably, the throttle valve actuating device (10) includes first energizing means (4) for energizing the throttle valve (3) in a closing direction and second energizing means (5) for energizing the throttle valve (3) in an opening direction, and maintains the throttle valve opening (TH) at a default opening (THDEF) by the first and second energizing means (4, 5) when the throttle valve (3) is not actuated by the actuating means (6).
With this configuration, the throttle valve is energized in the closing direction by the first energizing means and energized in the opening direction by the second energizing means. The throttle valve is maintained at the default opening when the actuating means is not actuating the throttle valve. Accordingly, even when a failure such that the actuating means does not operate normally has occurred, it is possible to supply air to the internal combustion engine, and run the vehicle which is driven by the internal combustion engine for evacuation. That is, a level of combustion within the engine is maintained to allow a driver to move the vehicle to a safe position upon failure of the actuating means.
Preferably, an output (DTH) of the controlled object model is defined based on the default opening (THDEF). In other words, the output of the controlled object model is defined as a difference between the throttle valve opening (TH) and the default opening (THDEF).
In the vicinity of the default opening, an actuating characteristic (dynamic characteristic) of the throttle actuating device changes abruptly. On the other hand, the controlled object model can most accurately indicates the dynamic characteristic of the controlled object in the vicinity of the reference output value of the controlled object model Therefore, by using the default opening as the reference output value, modeling accuracy of the controlled object model is improved, resulting in better controllability.
Preferably, the control system further includes identifying means (22) for identifying at least one model parameter (a1, a2, b2, c1) of the controlled object model, and the control means controls the throttle valve actuating device (10) using the at least one model parameter (a1, a2, b2, c1).
With this configuration, the throttle valve actuating device is controlled using one or more identified model parameter. Accordingly, good controllability of the control can be maintained even when the dynamic characteristic of the throttle valve actuating device has changed due to aging, or the environmental condition has changed.
Preferably, the control means (21) controls the throttle valve actuating device (10) with a sliding mode control.
With this configuration, the throttle valve actuating device is controlled with the sliding mode control. Since the sliding mode control has strong robustness, good controllability of the throttle valve opening to the target opening can be obtained even in the presence of the modeling error (a difference between the actual characteristics of the throttle valve actuating device and the characteristics of the controlled object model). In addition, the control is more stabilized.
Preferably, the control input (Usl) from the control means (21) to the throttle valve actuating device (10) includes an adaptive law input (Uadp).
With this configuration, better controllability is obtained even in the presence of disturbance and/or the modeling error.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate embodiments of the present invention by way of example.